DESCRIPTION: Juvenile rheumatoid arthritis (JRA) is the most common chronic inflammatory arthritis of childhood. The end result of ongoing synovial inflammation is degradation of articular cartilage. Whether the control of synovitis halts further cartilage degradation is not known. Irreversible thinning and erosion of cartilage leads to significant morbidity and loss of function. Magnetic resonance imaging (MRI) is proven to be a useful modality for depicting articular cartilage and synovium in both children and adults with inflammatory arthritis. Quantitative T2 mapping of articular cartilage in adults has shown that increased T2 relaxation time is an early marker of cartilage injury. This application will test the hypothesis that increased T2 relaxation time in articular cartilage of the knee in children with JRA reflects early cartilage injury. This quantitative method might possibly detect potentially reversible articular cartilage changes prior to irreversible cartilage erosions detected by conventional MRI. The longitudinal relationship between serial short-term changes in articular cartilage T2 relaxation time, degree of synovial inflammation, and clinical evaluation of disease activity will be determined. Articular cartilage T2 relaxation time in children with limited disease duration undergoing therapy will be quantified and monitored for reversibility. Serum and synovial fluid biomarkers will be measured and compared with alterations in articular cartilage T2 relaxation time. We will determine whether changes in T2 relaxation time profiles are predictive of articular cartilage erosions in children with JRA, and quantify and monitor reversibility of articular cartilage T2 relaxation time changes in children with longer disease duration. The long-term goal of this research is to provide a noninvasive, quantitative measure of early and potentially reversible degeneration in articular cartilage of children. These studies may extend the utility of MRI to quantitatively validate clinical outcomes in rheumatic diseases.